1. Field of the Invention
The present invention relates to an image layout apparatus and, more particularly, to an image layout apparatus for performing a layout, e.g., coloring, a modification of a pattern, and the like, of an original image in accordance with mark image data designated by, e.g., a color frame mark on the original image.
2. Description of the Related Art
A system for editing a monochromatic original image using a color mark is known ("Original Editing System Using Facsimile" Society of Electronics and Communications Letters, '80/12 Vol. J63-D 12). In this system, a color mark designating a content to be laid out is written on a black-and-white image a color mark using a red ink, a mark portion is discriminated from an image signal obtained by reading an original image by a color scanner, and an image designated by the mark is automatically laid out.
Such an image layout operation is popularly applied to image coloring layout operations. In the coloring layout operation, a color mark enclosing a given area is written on an original, and an image inside the color mark area is colored. For example, Published Unexamined Japanese Patent Application No. 57-185767 describes its example. An area designation method using a color mark has the following advantages. That is, an area in a desired pattern can be easily designated as compared to area designation using a tabulator, a coordinate input device, or the like, cumbersome operations for, e.g., replacing originals, measuring the position of an area on an original, and the like need not be performed, and so on.
In order to perform such an image layout operation, a mark image signal corresponding to, e.g., a color frame mark for designating a layout range and a to-be-laid-out image signal corresponding to, e.g., a monochromatic image portion to be laid out must be discriminated and separated from an input image signal obtained by reading an original. In this case, the mark image signal need not have a high resolution since it is data indicating a boundary of an area to be colored, and it is rather important that the mark image signal allows rough recognition of connection, and is not easily influenced by noise. On the other hand, it is important that the to-be-laid-out image signal keeps a high resolution since its image pattern is directly reflected in an output image.
In order to perform separation and discrimination of the mark image signal and the to-be-laid-out image signal, the following method is conventionally adopted. That is, a signal corresponding to a hue, a saturation, and a color difference, or the like is calculated from RGB image signals obtained by reading an image on an original to descriminate a color. If a chromatic color such as red, green, blue, or the like is detected, a color frame mark (mark image signal) is discriminated, and if an achromatic color such as black, gray, or the like is detected, a monochromatic image portion (to-be-laid-out image signal) is discriminated. As detailed methods of determining the mark image signal and the to-be-laid-out image signal, for example, a method of comparing a color difference signal with a given threshold value, and determining signals based on the relationship between the two signals, a method of directly looking up a look-up table on the basis of RGB image signals, and the like are known.
With these methods, however, it is difficult to perform image processing such as high frequency emphasis filtering of the to-be-laid-out image signal to obtain a high quality image since the to-be-laid-out image signal is converted into a binary signal indicating the presence/absence of a monochromatic image portion.
Meanwhile, in order to process a color image signal, a method of separating a color image signal into two signals, i.e., a hue signal and a density signal, and processing these signals is known (Published Unexamined Japanese Patent Application No. 63-10882). When this method is applied to image layout, the hue signal, for example, can be used as a mark image signal. However, the density signal is a signal representing a density of a hue represented by the hue signal, but does not represent a to-be-laid-out image signal itself. Therefore, this known technique cannot be applied to separatio and discrimination of a mark image signal and a to-be-laid-out image signal in an image layout apparatus.
As described above, according to the prior art techniques, when a mark image signal and a to-be-laid-out image signal are to be separated and discriminated, a color is discriminated from RGB image signals obtained by reading an original image by a color image sensor. If the discriminated color is a chromatic color, a color frame mark (mark image portion) is determined, and if the discriminated color is an achromatic color, a monochromatic image portion (to-be-laid-out image portion) is determined. Thus, the to-be-laid-out image signal becomes a binary signal indicating the presence/absence of a monochromatic image portion, and it is difficult to perform image processing such as high frequency emphasis filtering for obtaining a high quality image.